1. Field of the Invention
The present invention relates to a liquid crystal display; in particular, to a liquid crystal display having pixels with switching element design.
2. Description of the Related Art
In recent years, Liquid Crystal Display (LCD) has been widely employed in various electrical products because of its advantages in lightness, slimness, low radiation, reduced power consumption, presenting a significant trend of gradually replacing a conventional Cathode Ray Tube (CRT). LCD uses liquid crystal rotation to control the transparency in the display device, which needs to apply a wide angle of view technology to improve disadvantage of a narrow angle of view; whereas the increase in an angle of view causes reduction in contrast and a gray level error, which problems being inevitable along with the development of large scaled LCD.
Liquid crystal does not belong to categories of solid, liquid and gas states, which is a material between solid and liquid states; in terms of molecular arrangement, liquid crystal presents highly regular alignment, and for optical properties, liquid material has isotropic property, while solid crystal shows regularity in its structure; thus liquid crystal has a certain degree of freedom of liquid material, retaining special optical property of anisotropic similar to solid crystal, and presenting features of polarity and conductance. According to liquid crystal molecule arrangement, it can be classified into smectic liquid crystal, nematic liquid crystal and cholesteric liquid crystal. An alignment film is primarily made of Polyimide (PI) with a thickness between about 500 Å˜1000 Å; under rubbing actions or based on alignment process irradiated by ion beams, the alignment film generates long-chain Alkyl and long-chain Fluoroalkyl along the side chain or terminal of Polyimide, making liquid crystal molecules form a prescribed angle of inclination, referred as a present inclination angle, in a fixed direction according to the long-chain Alkyl and long-chain Fluoroalkyl. Before the alignment process, the side chains or terminals of Polyimide present an arbitrary arrangement; after the alignment process, whereas, under mechanical force or lighting, the side chains or terminals of Polyimide show a forward alignment in the alignment direction, and liquid crystal molecules accordingly form an arrangement at the preset inclination angle along the glass substrate.
Currently, amorphous silicon display devices use the twist nematic liquid crystal, in which the liquid crystal material of high resistance and high reliability employs an Np-typed liquid crystal mixture composed of fluorine series liquid crystal molecules and olefin series end groups, with there in such a liquid crystal mixture added a few percents of asymmetric optic active agent. Referring to FIG. 1 (prior art), an Optical Compensated Bend (OCB) disclosed in U.S. Pat. No. 6,933,916B2 is shown, wherein the pixel 1 of the liquid crystal display device comprises a gate line 11, a pixel area 12 and a protrusion 13. At present, in order to solve the issue of liquid crystal response rate, it is accomplished by presenting splay alignment while no voltage being applied, but becoming bend alignment while a certain voltage being applied (transition voltage). As the OCB uses such a bend alignment to perform switching actions, the time required for alignment change is shorter due to the flow effect in liquid crystal layer, and response speed rendered therein is significantly faster. It primarily uses the gate line 11 to divide the pixel area 12 into two electrical fields, enhancing electrical field power to enable uniform distribution of liquid crystal transformation in the pixel area 12 and to increase response speed of the liquid crystal phase transition. The protrusion 13 located on the gate line can control the liquid crystal transformation direction in these two electrical fields. The π cell of the general gap cell, the formation of bi-axial film, in conjunction with the feature of the wide angle of view in such a cell, it is hence possible to implement the capability of high gray-level display, and the response time for such a cell can be 10 times higher than general twist nematic (TN) cell, allowing a fast response speed of 2˜8 msec. Therefore, under the circumstances that all these conditions can be satisfied, it is possible to fully exploit the advantages of color technology, allowing liquid crystal display devices to realize the practice of no blurred image and obscure boundary. However, such a technology compromises at the price of size of opening rate in the pixel area. The present invention principally takes the opening rate in the pixel area 12 and the response speed of liquid crystal phase transition into consideration.
In view of the above-mentioned issues found in prior art, for appropriate resolutions thereof, the inventors of the present hereby propose a liquid crystal display device based on long-term professional researches and developments and experiences in field practice as the base for improving the drawbacks illustrated supra.